1. Technical Field
The present invention relates to a multiple sheet feed apparatus for a printer, which is capable of performing a sheet feed operation through arbitrarily selected one or more of a plurality of sheet feed mechanisms in the apparatus.
2. Background of the Prior Art
Conventionally, various sheet feed apparatuses of the dual type, having two feed systems mounted therein and each adapted to feed or transport a corresponding sheet of paper for printing, have been known. Examples of these are described in Japanese patent publication No. 58-394 and corresponding provisional patent publication No. 51-58125 (hereinafter, referred to as Prior Art Reference 1), Japanese provisional patent publication No. 51-59526 (Prior Art Reference 2), Japanese patent publication No. 57-50194 and corresponding provisional patent publication No. 53-42915 (Prior Art Reference 3), Japanese provisional patent publication No. 53-87807 (Prior Reference Art 4), and Japanese provisional patent publication No. 53-102122 (Prior Art Reference 5).
Prior Art 1, 2 References each disclose apparatus that comprises a first sheet feed roller secured to a sheet feed roller shaft, a second sheet feed roller secured to the roller shaft through a one-way clutch, and a first sheet feed driving means for driving the roller shaft, a second sheet feed driving means for driving the second feed roller, respectively. In these prior art arrangements, the one-way clutch is so arranged as to be locked or engaged when the roller shaft is rotatively driven by the first sheet feed driving means, and released or disengaged when the second feed roller is rotatively driven by the second sheet feed driving means. Accordingly, when the sheet feed roller shaft is rotated by the first sheet feed driving means, the first and second rollers are caused to rotate to simultaneously feed corresponding first and second sheets. On the other hand, when the second sheet feed roller is rotated by the second sheet feed driving means, only the second sheet alone is activated.
Prior Art Reference 3 comprises a journal sheet feed roller, a second sheet feed roller coupled to the journal sheet feed roller through a one-way clutch, a journal sheet feed roller driving means consisting of a ratchet wheel and feed pawls for driving the journal sheet feed roller, and a first sheet feed means disposed at a location facing an outlet to which a receipt sheet is delivered by the second sheet feed roller, wherein the one-way clutch is arranged so that it is locked when the journal sheet feed roller is rotatively driven by the journal sheet feed roller driving means, whereas the clutch is released when the receipt sheet is delivered by the first sheet feed means and causes the second sheet feed roller to rotate. In this prior art arrangement, when the journal sheet feed roller is rotated by the journal sheet feed roller driving means, the second sheet feed roller is also rotated for simultaneous delivery of both of the journal sheet and the receipt sheet, whereas, when the second sheet feed roller is merely driven by the first sheet feed means through the delivered receipt sheet, the journal sheet feed roller is rendered inoperative so that the receipt sheet alone is delivered.
Thus, the teaching of Prior Art Reference 3 is basically the same, in principle, as that of Prior Art References 1, 2. More specifically, the journal sheet feed roller, the second sheet feed roller, the journal sheet feed roller driving means and the first sheet feed means in Prior Reference Art 3 correspond to the first sheet feed roller, the second sheet feed roller, the first sheet feed driving means and the second sheet feed driving means in Prior Art References 1, 2, respectively.
Prior Art References 3 4 and 5 of the dual sheet feed system type each comprise two one-way clutches, each of which is mounted on a corresponding one of drive shafts of the respective sheet feed systems in a manner providing opposite directions of transmission of motion with respect to each other. Further, a motor for driving the drive shafts is provided, which is rotated in either forward or reverse direction to alternately render the two drive shafts effective, thereby switchingly and alternately delivering the sheets in the two systems.
Prior Art References 1-3 require two driving means for driving the two sheet feed systems juxtaposed in a printer to deliver the first and second sheets therethrough, and are thus complex in construction and high in cost and, furthermore, require a broad space for installation. Although these arrangments are capable of delivering both first and second sheets simultaneously, or only the second sheet, they cannot independently deliver the first sheet alone.
Prior Art References 4 and 5 merely require a single driving means, and are thus simple in construction and capable of independently delivering either of the sheets loaded in the respective feeding systems, as distinct from Prior Art References 1-3. However, Prior Art References 4, 5 have the drawback that the sheet feed seed is low in their operational mode of feeding both the sheets, because, in such mode, the motor is first rotated in the forward direction to deliver one of these sheets, and then rotated in the reverse direction for feeding another sheet, as mentioned above.